C / C ++malloc() vs new() in

malloc()

This functionmalloc()used to allocate the requested byte size and return a pointer to the first byte of the allocated memory. If it fails, it returns a null pointer.

This ismalloc()C ++language syntax,

pointer_name  =  (cast-type*)  malloc(size);

Here,

pointer_name-to any name for the pointer.

cast- type-You need to cast the data type of the allocated memorymalloc().

Size-the size of memory allocated in bytes.

This ismalloc()C language example,

Example

#include  <stdio.h>
#include  <stdlib.h>
int main()  {
　　　int  n  =　4,  i,　*p,  s  =  0;
　　　p  =  (int*)  malloc(n　*　sizeof(int));
　　　if(p == NULL) {}}
　　　　　　printf("\nError! Memory not allocated.");
　　　　　　exit(0);
　　　}
　　　printf("\nEnter elements of array: ");
　　　for(i = 0; i < n;　++i) {
　　　　　　scanf("%d", p　+　i);
　　　　　　s　+=　*(p　+　i);
　　　}
　　　printf("\nSum: %d", s);
　　　return 0;
}

This is the output,

Enter elements of array :　32　23　21　8
Sum :　84

In the above program, four variables are declared, one of which is a pointer variable* p, it stores the memory allocated by malloc. We are printing the sum of the elements.

int  n  =　4,  i,　*p,  s  =  0;
p  =  (int*)  malloc(n　*　sizeof(int));
if(p == NULL) {}}
　　　printf("\nError! Memory not allocated.");
　　　exit(0);
}
printf("\nEnter elements of array: ");
for(i = 0; i < n;　++i) {
　　　scanf("%d", p　+　i);
　　　s　+=　*(p　+　i);
}
printf("\nSum: %d", s);

New()

The new operator requests memory allocation on the heap. If there is enough memory available, it initializes the memory to a pointer variable and returns its address.

This is C ++The syntax of the new operator in the language,

pointer_variable = new datatype;

This is the syntax of initializing memory,

pointer_variable = new datatype(value);

This is the syntax of allocating a memory block,

pointer_variable = new datatype[size];

This is C ++of the new operator in a language,

Example

#include <iostream>
using namespace std;
int main () {
　　　int　*ptr1　= NULL;
　　　ptr1　= new int;
　　　float　*ptr2　= new float(223.324);
　　　int　*ptr3　= new int[28];
　　　*ptr1　=　28;
　　　cout << "Value of pointer variable　1　: " <<　*ptr1　<< endl;
　　　cout << "Value of pointer variable　2　: " <<　*ptr2　<< endl;
　　　if (!ptr3)
　　　cout << "Allocation of memory failed\n";
　　　else {
　　　　　　for (int i =　10; i <　15; i++)
　　　　　　ptr3[i] = i+1;
　　　　　　cout << "Value to store in block of memory: ";
　　　　　　for (int i =　10; i <　15; i++)
　　　　　　cout << ptr3[i] << " ";
　　　}
　　　return 0;
}

Output result

Value of pointer variable　1　:　28
Value of pointer variable　2　:　223.324
Value to store in block of memory:　11　12　13　14　15

In the above program, three pointer variables are declared as ptr1, ptr2and ptr3. The pointer variable ptr1and ptr2using value initialization,new()and ptr3Bynew()Method stores the allocated memory block.

ptr1　= new int;
float　*ptr2　= new float(223.324);
int　*ptr3　= new int[28];
*ptr1　=　28;